//====================demo=======================
//以下是一个简单的测试demo，如果不需要请删除
$rsa = new Rsa('sslkey'); //sslkey为存放密钥的路径，将已有的密钥文件复制到该路径下，公钥名称为pub.key，私钥名称为priv.key
$rsa->createKey(); //创建一对密钥，如果密钥对已经存在，不需调用
//私钥加密，公钥解密
echo 'source：<br />';
$pre = $rsa->privEncrypt('');
echo 'private encrypted:<br />' . $pre . '<br />';
$pud = $rsa->pubDecrypt($pre);
echo 'public decrypted:' . $pud . '<br />';
//公钥加密，私钥解密
echo 'source:干IT的<br />';
$pue = $rsa->pubEncrypt('干IT的');
echo 'public encrypt:<br />' . $pue . '<br />';
$prd = $rsa->privDecrypt($pue);
echo 'private decrypt:' . $prd;
//========================demo======================

<?php
/**
 * 使用openssl实现非对称加密
 *
 */
class Rsa
{
  /**
   * private key
   */
    private $_privKey;
    /**
     * public key
     */
    private $_pubKey;
    /**
     * the keys saving path
     */
    private $_keyPath;
    /**
     * the construtor,the param $path is the keys saving path
     */
    public function __construct($path)
    {
        if(empty($path) || !is_dir($path)){
            throw new Exception('Must set the keys save path');
        }
        $this->_keyPath = $path;
    }
    /**
     * create the key pair,save the key to $this->_keyPath
     */
    public function createKey()
    {
        $r = openssl_pkey_new();
        openssl_pkey_export($r, $privKey);
        file_put_contents($this->_keyPath . DIRECTORY_SEPARATOR . 'priv.key', $privKey);
        $this->_privKey = openssl_pkey_get_private($privKey);
        $rp = openssl_pkey_get_details($r);
        $pubKey = $rp['key'];
        file_put_contents($this->_keyPath . DIRECTORY_SEPARATOR . 'pub.key', $pubKey);
        $this->_pubKey = openssl_pkey_get_public($pubKey);
    }
    /**
     * setup the private key
     */
    public function setupPrivKey()
    {
        if(is_resource($this->_privKey)){
            return true;
        }
        $file = $this->_keyPath . DIRECTORY_SEPARATOR . 'priv.key';
        $prk = file_get_contents($file);
        $this->_privKey = openssl_pkey_get_private($prk);
        return true;
    }
    /**
     * setup the public key
     */
    public function setupPubKey()
    {
        if(is_resource($this->_pubKey)){
            return true;
        }
        $file = $this->_keyPath . DIRECTORY_SEPARATOR . 'pub.key';
        $puk = file_get_contents($file);
        $this->_pubKey = openssl_pkey_get_public($puk);
        return true;
    }
    /**
     * encrypt with the private key
     */
    public function privEncrypt($data)
    {
        if(!is_string($data)){
            return null;
        }
        $this->setupPrivKey();
        $r = openssl_private_encrypt($data, $encrypted, $this->_privKey);
        if($r){
            return base64_encode($encrypted);
        }
        return null;
    }
    /**
     * decrypt with the private key
     */
    public function privDecrypt($encrypted)
    {
        if(!is_string($encrypted)){
            return null;
        }
        $this->setupPrivKey();
        $encrypted = base64_decode($encrypted);
        $r = openssl_private_decrypt($encrypted, $decrypted, $this->_privKey);
        if($r){
            return $decrypted;
        }
        return null;
    }
    /**
     * encrypt with public key
     */
    public function pubEncrypt($data)
    {
        if(!is_string($data)){
            return null;
        }
        $this->setupPubKey();
        $r = openssl_public_encrypt($data, $encrypted, $this->_pubKey);
        if($r){
            return base64_encode($encrypted);
        }
        return null;
    }
    /**
     * decrypt with the public key
     */
    public function pubDecrypt($crypted)
    {
        if(!is_string($crypted)){
            return null;
        }
        $this->setupPubKey();
        $crypted = base64_decode($crypted);
        $r = openssl_public_decrypt($crypted, $decrypted, $this->_pubKey);
        if($r){
            return $decrypted;
        }
        return null;
    }
    public function __destruct()
    {
        @ fclose($this->_privKey);
        @ fclose($this->_pubKey);
    }
}